webdriver: Implement maximize window for both headless&headed window (#38271)

- Implement [Maximize
Window](https://w3c.github.io/webdriver/#maximize-window)
- Previously, headless window screen size is same as inner size if not
specified in preference. We make it double as required by the test to
not have max window initially.
- Some other random cleanup.

Testing: webdriver Stress test for maximize window (headed + headless).

---------

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

ports/servoshell/desktop/headless_window.rs

@@ -13,7 +13,7 @@ use servo::servo_geometry::{
     DeviceIndependentIntRect, DeviceIndependentPixel, convert_rect_to_css_pixel,
 };
 use servo::webrender_api::units::{DeviceIntPoint, DeviceIntRect, DeviceIntSize, DevicePixel};
-use servo::{RenderingContext, ScreenGeometry, SoftwareRenderingContext};
+use servo::{RenderingContext, ScreenGeometry, SoftwareRenderingContext, WebView};
 use winit::dpi::PhysicalSize;
 
 use super::app_state::RunningAppState;
@@ -47,7 +47,7 @@ impl Window {
 
         let screen_size = servoshell_preferences
             .screen_size_override
-            .map_or(inner_size, |screen_size_override| {
+            .map_or(inner_size * 2, |screen_size_override| {
                 (screen_size_override.to_f32() * hidpi_factor).to_i32()
             });
 
@@ -86,7 +86,7 @@ impl WindowPortsMethods for Window {
 
     fn request_resize(
         &self,
-        webview: &::servo::WebView,
+        webview: &WebView,
         outer_size: DeviceIntSize,
     ) -> Option<DeviceIntSize> {
         let new_size = DeviceIntSize::new(
@@ -167,4 +167,17 @@ impl WindowPortsMethods for Window {
     fn rendering_context(&self) -> Rc<dyn RenderingContext> {
         self.rendering_context.clone()
     }
+
+    fn maximize(&self, webview: &WebView) {
+        self.window_position.set(Point2D::zero());
+        self.inner_size.set(self.screen_size);
+        // Because we are managing the rendering surface ourselves, there will be no other
+        // notification (such as from the display manager) that it has changed size, so we
+        // must notify the compositor here.
+        webview.move_resize(self.screen_size.to_f32().into());
+        webview.resize(PhysicalSize::new(
+            self.screen_size.width as u32,
+            self.screen_size.height as u32,
+        ));
+    }
 }